1. Field of the Invention
The present invention relates to the structure of a pipe plate unit for heat exchangers and the method of replacement for said the pipe plate unit, which is comprised of a fluid chamber formed on one side of each of two pipe plates, and a plurality of heat conducting pipes affixed by welding to both edges of said pipe plates, wherein such heat exchangers may be employed in condensers, etc. that used in thermoelectric and nuclear power plants.
2. Description of the Related Arts
FIG. 8 shows a diagram of the principal structure of a condenser 200 such as was conventionally used in thermoelectric and nuclear power plants. In the figure, 203 represents a condenser casing, 206 a condensation chamber in the below described pipe plate unit, and 202 a water chamber with and inlet/outlet for sea water. 201 represents a pipe plate unit comprising two pipe plates 1, 1, one side of each bordering the foregoing water chambers 202, with a plurality of heat conducting pipes 4 being affixed by welding thereto. 5 is a pipe support plate supporting a plurality of said heat conduction pipes 4.
In condensers of the prior art, the heat conducting pipes made from titanium materials were proposed for use as the foregoing heat conducting pipes.
In these pipe plate units 201 equipped with the titanium heat conducting pipes 4, the pipe plates 1 were commonly made from carbon steel materials or the like in order to hold down the cost of materials, to which a surface plate (faceplate) of titanium materials was affixed by explosive cladding, etc. This material is called clad steel plate.
In such condenser for conventional thermoelectric or nuclear power plants shown in FIG. 8, when the heat conducting pipes 4 wore out as the plant facilities aged, if the heat conducting pipes 4 that performed the heat exchange, pipe plates 1 and pipe support plates 5, were to be manufactured as a pipe plate unit 201 in a factory and be replaced as a single module, it would be possible to reduce construction time as well as costs.
However, due to the structure of condenser 200, when replacing pipe plate unit 201, it would be necessary to install pipe plate unit 201 from the side of condenser 200.
But as is shown in FIG. 8, since the condenser 200 is normally installed just beneath a low pressure turbine, all or the majority of pipe plate units 201 are located beneath the floor 204 of the plant.
Thus, because pipe plate unit 201 has a large number of heat conducting pipes 4 welded to its pipe plates 1, because of the three dimensional assembly of said pipe plate unit 201, and because all or most of pipe plate unit 201 would lie beneath the foregoing plant floor 204 level, interference by the foundation 205 with pipe plate unit 201 made it impossible to install said pipe plate unit 201 into condenser 200 in a fully assembled form.
Due to this problem, the conventional solution did not use a factory module, but rather, the parts required for the replacement, such as the pipe support plates 5 and the pipe plates 1 would be placed inside of the condenser casing 203 on site, and then heat conducting pipes 4 would be inserted one by one through pipe plates 1 and pipe support plates 5, and subsequently be welded to pipe plates 1. Accordingly, this conventional means, further hampered by the poor working environment on site, required a great many construction steps to swap out heat conducting pipes 4 and the other parts of pipe plate unit 201, and the costs for these replacement operations were high.
Also, prior to the present invention, the preceding technology shown in FIGS. 9 and 10 were disclosed in Japan Patent Publication 2001-201271.
As is shown in FIGS. 9 and 10, the condenser in the preceding technology, installed in nuclear power plants, etc., was comprised of a unit casing 301 that retained a pipe plate holding a large number of small, pipe-shaped cooling tubes. Said unit casing 301 was an assembly consisting of the water chamber bodies 306a, 306b, the water chamber covers 307a, 307b which comprised the input side water chamber 308a, and the outlet side water chamber 308a was sandwiched between pipe plates. At the lower edge of the foregoing input side water chamber 308a was installed a coolant inlet seat 311a, while coolant inset seat 311b was installed at the lower edge of outlet side water chamber 308a. 
Accordingly, as shown in FIGS. 9 and 10 the pipe bundles that are attached inside of the condenser unit casing 301 in a manner such that a plurality of the pipe bundle units run parallel to the flow of steam S. In other words, the plurality of short pipe bundle units 323 (or as shown in FIG. 10, 323a) run parallel to steam flow along the plate surface of connection plate 325.
Thus, in this preceding technology, since the ends of coolant pipes 302 are affixed to connection plate 325, these unitized pipe bundles 323 or 323a can be separately attached inside of the casing 1, and further, since the other end of the foregoing unit pipe bundles 323 or 323a is attached to pipe plates 324, there are solidly affixed on the side next to the water chambers 308a and 308b. 
With this technology, if there are any obstacles inside the structure in which the units are transported or any restrictions upon the openings through which they are transported, there remains enough space to withdraw the coolant pipes 2, and even in difficult installations such as condensers, they are easily pulled out and replaced to shorten the time required for the construction operation.
Moreover, as shown in the foregoing FIG. 8, when pipe plate units 201 which includes heat conducting pipes 4 are installed beneath the lower pressure turbine in a condenser, all or most of the pipe units lie below the floor grade 204 of the plant.
At this point, preceding technology disclosed in Japan Patent Publication 2001-201272, as shown in FIGS. 9 and 10, individually install a plurality of pipe bundle units 323 or 323a inside the condenser casing in a direction parallel to the flow of steam S, but although each of the pipe bundle units 323 or 323a needs to be moved in the direction of steam S flow, in other words in the vertical direction, for their installation or removal, it is not possible to move pipe bundles 323 or 323a in the horizontal direction. Thus in swapping out the pipe plate units, the entire condenser must be lifted up to clear the interference from the foundation 205 to perform the exchange. Accordingly, this technique also involves a great many construction steps to complete the exchange of the pipe plate units, and those operations are costly.